Announcements Precipitation lab write-up due tomorrow at the start of discussion Text HW due tomorrow in discussion Lon-capa HW #4 Type 1 due Monday, Oct 15 th at 7:00pm Lon-capa HW #4 Type 2 due Wednesday, Oct 17 th at 7:00pm
Last Lecture K 2 SO 4 (aq) + Ba(NO 3 ) 2 (aq) AgNO 3 (aq) + KCl(aq) NaNO 3 (aq) + KCl(aq) What will happen when these are mixed together?
Determine products K 2 SO 4 (aq) + Ba(NO 3 ) 2 (aq) Products: BaSO 4 + KNO 3 AgNO 3 (aq) + KCl(aq) Products: AgCl + KNO 3 NaNO 3 (aq) + KCl(aq) Products: NaCl + KNO 3
Write balanced equations K 2 SO 4 (aq) + Ba(NO 3 ) 2 (aq) BaSO 4 + 2KNO 3 AgNO 3 (aq) + KCl(aq) AgCl + KNO 3 NaNO 3 (aq) + KCl(aq) NaCl + KNO 3
Solubility Rules (Page 172) 1. Most nitrate salts are soluble. 2. Most salts of sodium, potassium, and ammonium cations are soluble. 3. Most chloride salts are soluble. Exceptions: Ag + and Pb 2+. 4. Most sulfate salts are soluble. Exceptions: Ca 2+, Ba 2+, and Pb 2+. 5. Most hydroxide salts are only slightly soluble. Soluble ones are: Na +, K +, and Ca 2+. 6. Most sulfide, carbonate, and phosphate salts are only slightly soluble.
Precipitation Reactions Know how to use the solubility rules (you will be given them on the exam). Know how to write equations from reactants (ionic reactants). Understand what solutions look like at a very magnified level.
Solubility rules K 2 SO 4 (aq) + Ba(NO 3 ) 2 (aq) BaSO 4 + 2KNO 3 BaSO 4 : Exception to rule#4 Solid KNO 3 : Nitrate salts (rule#1) Potassium salts (rule #2) Soluble (no solid) Solubility Rules Most nitrate salts are soluble. Most salts of sodium, potassium, and ammonium cations are soluble. Most chloride salts are soluble. Exceptions: Ag + and Pb 2+. Most sulfate salts are soluble. Exceptions: Ca 2+, Ba 2+, and Pb 2+. Most hydroxide salts are only slightly soluble. Soluble ones are: Na +, K +, and Ca 2+. Most sulfide, carbonate, and phosphate salts are only slightly soluble.
Solubility rules AgNO 3 (aq) + KCl(aq) AgCl + KNO 3 AgCl Exception to rule #3 Solid KNO 3 Nitrate salts (rule#1) Potassium salts (rule #2) Soluble (no solid) Solubility Rules Most nitrate salts are soluble. Most salts of sodium, potassium, and ammonium cations are soluble. Most chloride salts are soluble. Exceptions: Ag + and Pb 2+. Most sulfate salts are soluble. Exceptions: Ca 2+, Ba 2+, and Pb 2+. Most hydroxide salts are only slightly soluble. Soluble ones are: Na +, K +, and Ca 2+. Most sulfide, carbonate, and phosphate salts are only slightly soluble.
Clicker #1 When potassium chloride and sodium nitrate are mixed, what precipitate will form? KCl (aq) + NaNO 3(aq) A) KNO 3 B) NaCl C) KCl D) NaNO 3 E) No precipitate will form. Solubility Rules Most nitrate salts are soluble. Most salts of sodium, potassium, and ammonium cations are soluble. Most chloride salts are soluble. Exceptions: Ag + and Pb 2+. Most sulfate salts are soluble. Exceptions: Ca 2+, Ba 2+, and Pb 2+. Most hydroxide salts are only slightly soluble. Soluble ones are: Na +, K +, and Ca 2+. Most sulfide, carbonate, and phosphate salts are only slightly soluble.
Example KCl(aq) + NaNO 3 (aq) KNO 3 + NaCl KNO 3 Nitrate salts (rule#1) Potassium salts (rule #2) Soluble (no solid) NaCl Sodium salts (rule #2) Chloride salts (rule #3) Soluble (no solid) Has a reaction occurred? Solubility Rules Most nitrate salts are soluble. Most salts of sodium, potassium, and ammonium cations are soluble. Most chloride salts are soluble. Exceptions: Ag + and Pb 2+. Most sulfate salts are soluble. Exceptions: Ca 2+, Ba 2+, and Pb 2+. Most hydroxide salts are only slightly soluble. Soluble ones are: Na +, K +, and Ca 2+. Most sulfide, carbonate, and phosphate salts are only slightly soluble.
What makes a chemical reaction? Bonds in reactants have to be broken Atoms rearrange Bonds form to make products
3 ways to write a reaction: Molecular equation How we ve written them up to this point Complete ionic equation shows what s happening in the solution; write it as appears in solution Net ionic equation what takes part in the chemical reaction; Remove spectator ions (don t do anything; only there to balance charges!)
Reaction of AgNO 3 and KCl Molecular Equation: AgNO 3 (aq) + KCl(aq) KNO 3 (aq) + AgCl(s) Complete Ionic Equation: Ag + (aq) + NO 3- (aq) + K + (aq) + Cl - (aq) K + (aq) + NO 3- (aq) + AgCl(s) Net Ionic Equation: Ag + (aq) + Cl - (aq) AgCl(s)
A Microscopic Look
Reaction of K 2 SO 4 and Ba(NO 3 ) 2 Molecular equation K 2 SO 4 (aq) + Ba(NO 3 ) 2 (aq) BaSO 4 (s) + 2KNO 3 (aq) Complete ionic equation 2K + (aq) + SO 4 2- (aq) + Ba 2+ (aq) + 2NO 3- (aq) BaSO 4 (s) + 2K + (aq) + 2NO 3- (aq) Net ionic equation SO 4 2- (aq) + Ba 2+ (aq) BaSO 4 (s)
A Microscopic Look
Mixing NaNO 3 and KCl Molecular equation: NaNO 3 (aq) + KCl(aq) NaCl(aq) + KNO 3 (aq) Complete ionic equation: Na + (aq) + NO 3- (aq) + K + (aq) + Cl - (aq) Na + (aq) + Cl - (aq) + K + (aq) + NO 3- (aq) all spectator ions no net ionic equation which means no chemical reaction occurred!
A Microscopic Look
Clicker #2 When aqueous silver nitrate and aqueous sodium chromate are mixed, what are the formulas of the products? A) Na 2 NO 3 and AgCrO 4 B) NaNO 3 and Ag 2 CrO 4 C) NaNO 3 and AgCrO 4 D) Na 2 NO 3 and AgCr 2 O 7 E) NaNO 3 and Ag 2 Cr 2 O 7
Demo Silver nitrate and sodium chromate AgNO 3 (aq) + Na 2 CrO 4 (aq) Ag 2 CrO 4 + NaNO 3 How to balance this equation? 2AgNO 3 (aq) + Na 2 CrO 4 (aq) Ag 2 CrO 4 + 2NaNO 3 What happens when the two solutions are mixed together?
Example 2AgNO 3 (aq) + Na 2 CrO 4 (aq) Ag 2 CrO 4 + 2NaNO 3 Ag 2 CrO 4 Not in rules! NaNO 3 Nitrate salts (rule#1) Sodium salts (rule #2) Soluble (no solid) Since NaNO 3 is soluble, the solid must be Ag 2 CrO 4 Solubility Rules Most nitrate salts are soluble. Most salts of sodium, potassium, and ammonium cations are soluble. Most chloride salts are soluble. Exceptions: Ag + and Pb 2+. Most sulfate salts are soluble. Exceptions: Ca 2+, Ba 2+, and Pb 2+. Most hydroxide salts are only slightly soluble. Soluble ones are: Na +, K +, and Ca 2+. Most sulfide, carbonate, and phosphate salts are only slightly soluble.
Reaction of AgNO 3 and Na 2 CrO 4 Molecular Equation: 2AgNO 3 (aq) + Na 2 CrO 4 (aq) Ag 2 CrO 4 (s) + 2NaNO 3 (aq) Complete Ionic Equation: 2Ag + (aq) + 2NO 3- (aq) + 2Na + (aq) + CrO 4- (aq) 2Na + (aq) + 2NO 3- (aq) + Ag 2 CrO 4 (s) Net Ionic Equation: 2Ag + (aq) + CrO 4 2- (aq) Ag 2 CrO 4 (s)
A Microscopic Look
Mixing Acids and Bases Sodium hydroxide and hydrochloric acid NaOH(aq) + HCl(aq) NaCl + H 2 O What happens when the two solutions are mixed together? No solid formed! So does that mean that no reaction occurred?
Mixing Acids and Bases Molecular equation: NaOH(aq) + HCl(aq) NaCl(aq) + H 2 O(l) Complete ionic equation: Na + (aq) + OH - (aq) + H + (aq) + Cl - (aq) Na + (aq) + Cl - (aq) + H 2 O(l) Net ionic equation: OH - (aq) + H + (aq) H 2 O(l)
Clicker #3 Is the resulting net ionic equation a chemical reaction? H + (aq) + OH (aq) H 2 O (l) A) Yes. There is a new compound formed from H + and OH. B) Yes. Whenever two compounds are mixed, a chemical reaction always occurs. C) No. A precipitate (solid) must be formed to be considered a chemical reaction. D) No. There was no color change so a chemical reaction did not occur.
What makes a chemical reaction? Bonds in reactants have to be broken Atoms rearrange Bonds form to make products
A Microscopic Look
Clicker #4 Will the resulting solution conduct electricity? A) No. There is no precipitate formed and a solid is required to conduct electricity. B) No. The resulting solution is pure water which does not conduct electricity. C) Yes. The resulting solution is pure water which conducts electricity. D) Yes. The resulting solution contains ions which conduct electricity.
Acids and Bases Molecular equation: Ba(OH) 2 (aq) + H 2 SO 4 (aq) BaSO 4 (aq) + 2H 2 O(l) Complete ionic equation: Ba 2+ (aq) + 2OH - (aq) + 2H + (aq) + SO 4 2- (aq) BaSO 4 (s) + H 2 O(l) Net ionic equation: Ba 2+ (aq) + 2OH - (aq) + 2H + (aq) + SO 4 2- (aq) BaSO 4 (s) + H 2 O(l)
A Microscopic Look
Clicker #5 Will the resulting solution conduct electricity? A) No. There is no precipitate formed and a solid is required to conduct electricity. B) No. The resulting solution is pure water which does not conduct electricity. C) Yes. The resulting solution is pure water which conducts electricity. D) Yes. The resulting solution contains ions which conduct electricity.
Concentration and Molarity What does concentration tell us? Quantity per volume (ratio!) Density: mass of substance per volume of solid or liquid (or solution) Molarity: number of moles of species per volume of aqueous solution
Clicker #6 Which of the three solutions is the most concentrated? A) Solution #1 B) Solution #2 C) Solution #3 D) The concentrations are the same.
Concentration and Molarity Which liquid is the most concentrated (has the most food coloring)? They are all the same! While the volumes are different, the RATIO of food coloring per volume is still the same
Concentration and Molarity How could we change the concentration then? Add more food coloring higher concentration Remove water by evaporation higher concentration Add more water lower concentration
Concentration and Molarity Think about what concentration means before getting lost in the math Solutions are always homogeneous!
Concentration and Molarity Start with 12 particles in 6.0L water 12/6.0 6/3.0L 2/1.0 2/6.0 = 2 = 2 = 2 = 1/3
Molarity Concentration of solution molarity Molarity = (moles of solute) / (liters of solution) has units of moles per liter (moles/l) Solute is whatever is being dissolved into solution
Announcements Precipitation lab write-up due tomorrow at the start of discussion Text HW due tomorrow in discussion Lon-capa HW #4 Type 1 due Monday, Oct 15 th at 7:00pm Lon-capa HW #4 Type 2 due Wednesday, Oct 17 th at 7:00pm